Method of applying a quantity of indium to the inner wall of a lamp bulb

ABSTRACT

A METHOD OF ATTACHING A QUANTITY OF INDIUM MATERIAL TO THE INNER WALLS OF A LAMP BULB, BY URGING THE MATERIAL AGAINST THE WALL WITH A ROLLER AND MOVING THE ROLLER CLOCKWISE AND COUNTER-CLOCKWISE ALTERNATELY.

April 71 o. KOLKMAN AL METHOD 0F APPLYING A QUANTITY OF INDIUM THE INNER WALL OF A LAMP BULB Filed Feb. 2. 1968 I VVM INVENTORS' mm: KOLKMAN ADOLF .1. DE VISSER ooFmEus .1. AG. HECK ENT United States Patent 3,574,033 METHOD OF APPLYING A QUANTITY OF INDIUM TO THE INNER WALL OF A LAMP BULB Dirk Kolkman, Adolf Jan de Visser, and Cornelis Johannes Adrianus Gerardus Heck, Emmasingel, Eindhoven, Netherlands, assignors to U.S. Philips Corporation, New York, N.Y.

Filed Feb. 2, 1968, Ser. No. 702,626 Claims priority, application Netherlands, Feb. 11, 1967, 6702109 Int. Cl. C09j /00 U.S. Cl. 156--306 4 Claims ABSTRACT OF THE DISCLOSURE A method of attaching a quantity of indium material to the inner walls of a lamp bulb, by urging the material against the wall with a roller and moving the roller clockwise and counter-clockwise alternately.

The invention relates to a method of applying a quantity of a material mainly containing indium to at least one point on the inner wall of the glass bulb for an indiumamalgam lamp or like. Such a method is known.

In the known method, a quantity of indium is liquefied by heating and is brushed on a given area of the inner surface of the bulb to which it then adheres in the form of a thin layer; the free surface of this layer is comparatively rough, which results in the formation of stripes extending in the longitudinal direction of the bulb when, during the manufacture of a lamp, a suspension of a fluorescent powder flows through the bulb. The relevant layer further has an irregular periphery so that the other appearance of the bulb is less aesthetic.

The invention has for its object to provide a method of applying in a simple manner a quantity of a material mainly containing indium, with both a satisfactory adhesion of the materail to the bub wall, and an aesthetic outer appearance, without heating and without the use of separate fastening materials.

The method according to the invention is characterized in that this material is applied in the form of a disc of preferably 20 to 60 microns thickness, by rolling to the inner wall of the bulb. Consequently, the starting disc is effectively rubbed against the inner wall of the bulb and then 'adheres thereto.

In one embodiment of the method according to the invention, the rolling process is continued at least until the junction layer between the disc and the wall of the bulb is completely or substantially completely free of gas. It is desirable that no air should be present in the junction layer between the disc and the bulb wall during the sintering treatment, to which the lamp vessel for an indium-amalgam lamp or the like is to be subjected afterwards; because this air may expand at the high sintering temperature so that the relevant disc is partly blown up and detached from the bulb wall.

The rolling :process should be carried out by means of a roller to be introduced into the tube. If use is made of a metal rolling member, the disc is found to be practically always detached from the bulb wall and to adhere to the surface of the roller after the rolling process. It has been found that this can be avoided if the outer layer of the roller consists of a synthetic resin based on polyamide.

It has further been found recommendable that a small quantity of a material melting at a temperature higher ice than 600 C., for example, germanium and/ or aluminium, should be added to the indium-containing material. Thus, the situation is avoided where the disc carefully applied to the bulb wall by the rolling process, flows away to one side of the cross-section of the bulb wall during the further treatments of the lamp vessel, in which high temperatures may be used, and that the contours and/or the smoothness of the surface of the disc are adversely affected. In practice, a quantity of a few percent of germanium and/ or aluminium is already found to be sufficient. This quantity forms, so to say, a reinforcing grating in which the liquefying indium-containing material is held in place. The invention also relates to a bulb for an indium-amalgam lamp treated by the method according to the invention.

The invention will be briefly described with reference to a diagrammatic drawing, in which FIGS. 1 and 2 are a longitudinal sectional view and a side elevation, respectively, of a simple arrangement for rolling out a disc of indium.

This arrangement comprises two rollers 1 and 3 which support a tubular glass bulb 5 to be treated. Reference numeral 7 denotes a rolling member made of a synthetic resin commercially available under the name of nylon which is rotatably arranged on the thin part 9 of a shaft 11. This rolling member has a smooth cylindrical surface. The shaft 11 is secured in a pressure member 13 which is adapted to move in the direction of height, for example, by pneumatic agency. A countersupport 15 is fixedly arranged above the roller 7 which has a smooth surface and is adapted to move in the direction of height; this countersupport comprises two plates 8 and 10 in which rollers 12 and 14 are secured.

A quantity of indium-containing material to be applied to a given area of the inner wall 17 of the bulb 5 is disposed in the form of a round disc 19 on the upper side of the rolling member 7, the pressure member 13 and countersupport 15 being moved away from each other. Subsequently, the glass bulb 5 is placed on the rollers 1 and 3. The pressure member 13 is then moved upwards and the bulb is lifted from the rollers, while the countersupport 15 is pressed against the rollers 12 and 14. The bulb 5 is then moved a few times to and fro in the direction of the double arrow 21 about its own longitudinal axis. It has been found that by this process the disc 19 can be applied to the inner wall 17 by rolling, that the air present in the junction layer between the disc 19 and the inner wall 17 is expelled and that the disc firmly adheres to the wall. Thus, the situation is avoided where air present in this junction layer expands at the comparatively high temperatures used in the sintering operations carried out afterwards, which would cause the disc to be detached from the wall.

The disc contains besides the main constituent indium, approximately 4% of germanium or aluminium, as a result of which the melting temperature of the disc is considerably raised. Thus, also avoided is the situation where at the high processing temperatures during the manufacture of indium-amalgam lamps, a disc once applied is caused to flow out.

What is claimed is:

1. A method of attaching a quantity of indium material to at least one area of the inner wall of a glass bulb of a lamp such as an indium-amalgam lamp, comprising disposing the material between said area and a roller having an outer layer of a synthetic resin based on polyamide, urging the roller and the bulb wall toward each other with said material between the roller and wall, and moving both the roller about its axis and said wall, with material in pressure contact therebetween, thereby urging the material against the wall to which it becomes adhered.

2. A method according to claim 1 further comprising adding to the indium a quantity of another material such as germanium and aluminum, having a melting temperature higher than 600 C.

3. A method according to claim 1 wherein moving said roller and wall comprises rotating each about their re- 1 References Cited UNITED STATES PATENTS 1,279,655 9/1918 Choate 156-233 1,406,538 2/1922 ChOate l56233 FOREIGN PATENTS 759,200 10/1956 Great Britain 1561 0 REUBEN EPSTEIN, Primary Examiner U.S. Cl. X.R. 

